Got a new passport last Friday.  WP expires at the end of April.   Can I just wait and go to Immigration on the 30th and do everything at once?  

 

The less stuff in my new passport the better.  

 

 

You can do the stamp transfer and the extension during one trip to immigration. The stamp transfer would be done before the extension is done. You could do the extension now instead of waiting until the end of the month.

You would get your new work permit at the Labor Ministry.